The following relates to the optoelectronic, electro-optical, display, light-switching, light phase modulation, and related arts.
Fast-response optical devices are of value in applications such as field-sequential display technologies, three-dimensional display technologies, and for various non-display technologies such as high-speed fiber optical communication systems. For such applications, high-speed optical devices such as variable phase retarders, multi-level (i.e. “gray scale”) attenuators, and optical shutters are of interest.
An optical shutter with high switching speed is described in Haven, “A liquid-crystal video stereoscope with high extinction ratios, a 28% transmission state, and one-hundred-microsecond switching”, in Proc. SPIE True 3D Imaging Techniques and Display Technologies vol. 761 pages 23-26 (1987). This device overcomes a typical problem with liquid crystal-based switching devices, namely that the transition created by applying voltage is much faster (of order tenths of a millisecond) than the transition created when the voltage is removed (relaxation, of order several milliseconds). The approach of Haven employs a pair of π-cells (see, e.g. Bos et al., Mol. Cryst. Liq. Cryst. Vol. 113, page 329 (1984)) whose rubbing directions are oriented orthogonally, sandwiched between fixed polarizer and analyzer elements. The total phase retardation is the difference between the phase retardations of the two constituent π-cells, and fast switching is achieved by relaxing both π-cells together to generate a zero phase shift and switching and holding voltage on only one π-cell to generate a phase shift of π (180°). When the two π-cells are relaxed together, the relaxation-versus-time curve is the same for both π-cells leading to zero total phase shift throughout the relaxation time.
The device of Haven is an optical shutter, and does not provide gray scale levels and is not useful in color display devices.